I love using Orbeez (gel beads that grow significantly in water) to light paint. They're like little marbles but with the index of refraction of water.
Here the Orbeez are standing still and I light painted above them.
And then I had to do a two-way camera rotation with the lit pond in my backyard.
Here I used two colors on separate cylindrical jars and waved a light behind them.
EDIT: This post contained digital art meant for another community that I posted here by mistake. My apologies. I changed this posts's content to fit with LP United guidelines.
For more examples of innovative and original light painting please give my light painting comrades a follow: @fadetoblack @dawnoner @mafufuma @fastchrisuk @martbarras @stefan.stepko @rod.evans.visual @yo-hoho @maxpateau and check out our Hive Community Lightpainters United